Influence of excess postexercise leucine ingestion on mTORC1 signaling and gene expression in skeletal muscle of older men: a 24 hr time‐course

Abstract

Essential amino acid (EAA) ingestion enhances postexercise muscle protein synthesis, and in particular leucine is thought to promote a greater stimulatory effect. The purpose of this preliminary study was to determine the effect of ingesting excess leucine following resistance exercise (RE) on skeletal muscle signaling and gene expression in older adults over a 24h time‐course. Older men performed a bout of RE and at 1h postexercise ingested 10g of EAA containing either a leucine content similar to high quality protein (CTRL, 1.8g leucine) or excess leucine (LEU, 3.5g leucine). Muscle biopsies (vastus lateralis) were obtained at basal and at 2, 5 and 24h postexercise for examination of mTORC1 signaling (western blot) and expression levels of genes (qPCR) involved with muscle growth (MyoD) and atrophy (MuRF‐1), amino acid transport (LAT1/SLC7A5, SNAT2/SLC38A2), and mitochondrial biogenesis (PGC‐1α). Both groups experienced similar increases in mTORC1 signaling and gene expression at 2 and 5h postexercise, which were more pronounced at 2h. However, at 24h postexercise LEU appeared to maintain higher expression levels of MyoD and amino acid transporters. These preliminary data suggest that excess leucine ingestion following RE may prolong the anabolic response and sensitivity to amino acids in skeletal muscle of older adults.NIAMS R01AR049877, NIA P30AG024832, NIH T32HD07539, NCRR 1UL1RR029876